Json.java

public void start(Future<Void> startFuture) {
	final Router router = Router.router(vertx);

	// Create a BodyHandler to have the capability to retrieve the body
	router.route().handler(BodyHandler.create());

	router.route(HttpMethod.POST, "/file").handler(routingContext -> {
		HttpServerResponse response = routingContext.response();

		// Retrieve the body as a JsonObject
		JsonObject body = routingContext.getBodyAsJson();
		// Get the filename attribute value
		String filename = body.getString("filename");

		// Execute a blocking part
		vertx.executeBlocking(future -> {
			byte[] bytes = parseLargeFile(filename);
			// Complete the future with the generated objects in the
			// blocking method
			future.complete(bytes);
		} , res -> {
			if (res.succeeded()) {
				// If the blocking part succeedeed
				byte[] bytes = (byte[]) res.result();

				response.putHeader("Content-Type", "application/octet-stream");
				response.setChunked(true);
				response.write(Buffer.buffer(bytes));
				response.setStatusCode(200);
				response.end();
			} else {
				// Otherwise we manage to return an error
				response.setStatusCode(500);
				response.setStatusMessage("Internal error: " + res.cause().getMessage());
				response.end();
			}
		});
	});

	vertx.createHttpServer().requestHandler(router::accept).listen(8080, result -> {
		if (result.succeeded()) {
			startFuture.complete();
		} else {
			startFuture.fail(result.cause());
		}
	});
}